Decrease of the resonance bandwidth of micromechanical oscillators by phase control of the driving force

A method for controlling the amplitude response of micromechanical oscillators is presented. The micromechanical oscillator is driven by two forces acting both in phase, a fixed sinusoidal force and a feedback force whose amplitude depends on the phase shift. This dependence exhibits a pronounced maximum when the phase shift is 90°, i.e., at the resonant frequency. Experiments performed with a microcantilever prove that this class of active control decreases the bandwidth of the amplitude response about two orders of magnitude. The noise of the microcantilever, mainly of a thermal nature, is not increased at resonance, and it is moderately increased at both sides of the amplitude peak. Moreover, the noise can be tuned by adjusting the ratio between the two driving forces.Peer reviewe

Sistema y procedimiento de inspección de superficies de estructuras micro y nanomecánicas

Sistema de inspección de superficies dispuesto para detectar características de desplazamiento relativo y/o de vibración de diversos puntos de una pluralidad de elementos (51) que forman parte de una estructura mecánica (5), comprendiendo dicho sistema: una fuente de luz (1) dispuesta para generar, al menos, un haz de luz (11); un detector sensible a la posición (2) dispuesto para recibir el haz de luz cuando es reflejado fuera de la estructura mecánica (5) y para generar, al menos, una señal de salida en respuesta a la recepción de dicho haz de luz; un sistema de control electrónico (3); un medio de exploración (4) para el desplazamiento relativo de dicho haz de luz con relación a la estructura mecánica (5) con el fin de explorar dicha estructura mecánica con el haz de luz, siguiendo las instrucciones del sistema de control electrónico (3); caracterizado porque dicho sistema de control electrónico (3) está dispuesto para controlar el medio de exploración (4) con el fin de desplazar el haz de luz por la estructura mecánica a lo largo de una primera trayectoria (A) con objeto de detectar una pluralidad de posiciones de referencia subsiguientes (C), cada una en un elemento, a lo largo de dicha primera trayectoria (A), en el que dicho sistema de control electrónico (3) está asociado operativamente con dicho detector sensible a la posición (2) para determinar dichas posiciones de referencia (C) como resultado de un análisis de, al menos, una señal de salida de dicho detector sensible a la posición (2); en el que dicho sistema de control electrónico (3) está dispuesto además para controlar el medio de exploración (4) para desplazar el haz de luz por la estructura mecánica a lo largo de una pluralidad de segundas trayectorias (B), estando asociada cada una de dichas segundas trayectorias (B) con una de dichas posiciones de referencia (C); dicho sistema de control electrónico está dispuesto además para obtener, durante el desplazamiento del haz de luz a lo largo de cada una de dichas segundas trayectorias (B), una pluralidad de salidas de señales de posición de dicho detector sensible a la posición (2).Peer reviewedConsejo Superior de Investigaciones Científicas (España)T3 Traducción de patente europe

Effect of the adsorbate stiffness on the resonance response of microcantilever sensors

The authors present a theoretical model to predict the resonance frequency shift due to molecule adsorption on micro- and nanocantilevers. They calculate the frequency shift experienced by cantilevers made of either silicon or the polymer SU-8, when two adsorbates, myosin protein and an alkanethiol, are attached to the cantilever surface. They demonstrate that the effect of the adsorbate stiffness can be comparable or even larger than the mass effect, producing positive frequency shifts. The results provide methods for decoupling both opposite effects and routes for the design of resonators with high sensitivity to molecule adsorption based on either stiffness or mass effects.Peer reviewe

Procedimiento de bioanálisis de moléculas de ácido nucleico en una muestra y biosensor para su implementación

Peer reviewedConsejo Superior de investigaciones CientíficasT3 Traducción de patente europe

Nanobiosensors based on optoelectronic and nanomechanical transducers for genomic and proteomic applications

5 páginas, 10 figuras.-- PACS: 42.25.-p; 42.82.-m; 85.85.+[EN] We show the design, fabrication and testing of micro/nanobiosensor devices based on highly sensitive optoelectronic and nanomechanical transducers. Most of the devices are fabricated by standard Silicon CMOS microelectronics technology according to a precise design for achieving a high sensitivity for biosensing applications. Three biosensors have been developed: (a) a Surface Plasmon Resonance biosensor, (b) an integrated, Mach-Zehnder micro/nano interferometer device based on optical waveguides, and (c) nanomechanical biosensors based on microcantilevers.[ES] En este artículo se muestra el diseño, la fabricación y la caracterización de dispositivos micro/nanobiosensores basados en transductores optoelectrónicos y nanomecánicos. La mayoría de los dispositivos se fabrican con tecnología estándar de Si compatible CMOS, después de un cuidadoso diseño de los transductores para conseguir biosensores de alta sensibilidad. Se muestran tres tipos de biosensors: (a) un biosensor de Resonancia de Plasmón Superficial (b) un micro/nano Ínterferómetro integrado Mach-Zehnder basado en guías de ondas ópticas y (c) biosensores nanomecánicos basados en micropalancas.Peer reviewe

A very low current scanning tunneling microscope

The applications of the scanning tunneling microscope (STM) in air are usually restricted to good conducting materials as clean metals, doped and passivated semiconductors, or to some molecular adsorbates deposited onto graphite. In order to study poor conducting materials as biological molecules, we have built a very low current STM. This instrument can routinely be operated at 0.1 pA while having a bandwidth of 7 kHz. The advantages of using very low currents are illustrated by imaging 5-nm-thick purple membranes. These membranes can only be imaged at currents smaller than 2 pA. © 1995 American Institute of Physics.DGICYT Nº.PB94-0016 .Peer Reviewe

Origin of the response of nanomechanical resonators to bacteria adsorption

Resonant microcantilevers are being actively investigated as sensitive mass sensors for biological detection. By performing experiments of adsorption of the bacteria Escherichia coli on singly clamped microcantilevers, we demonstrate that the effect of the added mass is not the only and may not be the main origin of the response of these sensors. The experiments show that the magnitude and sign of resonance frequency shift both depend critically on the distribution of the adsorbed bacterial cells on the cantilever. We relate this behavior to the added mass that shifts the resonance to lower frequencies and the higher effective flexural rigidity of the cantilever due to the bacteria stiffness that shifts the resonance to higher frequencies. Both effects can be uncoupled by positioning the cells where each effect dominates, near the free cantilever end for measuring the added mass or near the clamping for measuring the increase of flexural rigidity.One of the authors (D.R.) acknowledges the fellowship funded by the Autonomic Community of Madrid. This work was supported by the Spanish National Research Council (CSIC), Project No. 200550M056.Peer reviewe

Chemical sensors and biosensors in liquid environment based on microcantilevers with amplified quality factors

Póster presentado al 1st Senspol Workshop: SENSPOL European Thematic Network (EC Environmental and Climate Programma) Sensing Technologies for Contaminated Sites and Groundwater celebrado en Alcala de Henares (Madrid-España) en 2001.Peer reviewe

Physics of nanomechanical spectrometry of viruses

There is an emerging need of nanotools able to quantify the mechanical properties of single biological entities. A promising approach is the measurement of the shifts of the resonant frequencies of ultrathin cantilevers induced by the adsorption of the studied biological systems. Here, we present a detailed theoretical analysis to calculate the resonance frequency shift induced by the mechanical stiffness of viral nanotubes. The model accounts for the high surface-to-volume ratio featured by single biological entities, the shape anisotropy and the interfacial adhesion. The model is applied to the case in which tobacco mosaic virus is randomly delivered to a silicon nitride cantilever. The theoretical framework opens the door to a novel paradigm for biological spectrometry as well as for measuring the Young's modulus of biological systems with minimal strains.We acknowledge financial support from the Spanish Science Ministry (MINECO) through projects MAT2012-36197 and from European Research Council through Starting Grant NANOFORCELLS (ERC-StG-2011-278860).Peer Reviewe

Spatially Multiplexed Micro-Spectrophotometry in Bright Field Mode for Thin Film Characterization

Thickness characterization of thin films is of primary importance in a variety of nanotechnology applications, either in the semiconductor industry, quality control in nanofabrication processes or engineering of nanoelectromechanical systems (NEMS) because small thickness variability can strongly compromise the device performance. Here, we present an alternative optical method in bright field mode called Spatially Multiplexed Micro-Spectrophotometry that allows rapid and non-destructive characterization of thin films over areas of mm2 and with 1 μm of lateral resolution. We demonstrate an accuracy of 0.1% in the thickness characterization through measurements performed on four microcantilevers that expand an area of 1.8 mm2 in one minute of analysis time. The measured thickness variation in the range of few tens of nm translates into a mechanical variability that produces an error of up to 2% in the response of the studied devices when they are used to measure surface stress variations.The authors acknowledge the financial support by European Research Council through Starting Grant NANOFORCELLS (ERC-StG-2011-278860). P. M. Kosaka acknowledges funding from the Fundación General CSIC ComFuturo program. We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI